Aerodynamics thread

[MiG-29]

Helicopter is not a jet fighter. Repeating "vectors" over and over isn't going to make a jet fighter behaves like a helicopter. Thrust vectoring produces moment and doesn't add to lift, as your own sources have shown. Physics are physics.

Momentum is a vector quantity. As discussed in an earlier unit, a vector quantity is a quantity that is fully described by both magnitude and direction

So go and read more


Torque and angular momentum are actually vector
quantities. Angular momentum is conserved in both magnitude and direction in the
absence of external torque

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There are four forces that act on an aircraft in flight: lift, weight, thrust, and drag. The motion of the aircraft through the air depends on the relative size of the various forces and the orientation of the aircraft. For an aircraft in cruise, the four forces are balanced, and the aircraft moves at a constant velocity and altitude. Some modern fighter aircraft can change the angle of the thrust by using a movable nozzle. The ability to change the angle of the thrust is called thrust vectoring, or vectored thrust.

Forces are vector quantities having a magnitude and a direction. The resulting acceleration, velocity and displacement of the aircraft are also vector quantities which can be determined by Newton's second law of motion and the rules of vector algebra. There are two component equations for the force on an aircraft. One equation gives the the net vertical force Fv, and the other gives the net horizontal force Fh. If we denote the thrust by the symbol T, the lift by L, the drag by D, and the weight by W, the usual force equations for an aircraft in level flight are:

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With new mechanical systems it is possible to deflect the engine exhaust from the nozzle and cant the thrust vector at an angle. We will call this angle c. The resulting force equations are shown on the slide:

Vertical: L - W + T sin(c) = Fv

Horizontal: T cos(c) - D = Fh

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[MiG-29]

Hey Engineer, just out of curiosity, does a thrust components cause by thrust vectoring can inhibit flight by disturbing the aircraft's center-of-gravity therefore causing it to be dist-able?

The resultant of a vector in Thrust vectoring is
Vertical: L - W + T sin(c) = Fv

One equation gives the the net vertical force Fv, and the other gives the net horizontal force Fh. If we denote the thrust by the symbol T, the lift by L, the drag by D, and the weight by W.

If you notice that is a sum of vectors, or momenta sum of vectors of the aircraft momentum.


can it? yes it can but for that aircraft have flight control system that swivel the nozzles accordingly along the aerodynamic surfaces.

Thrust vectoring increases turn rate simply becasue
Therefore to change momentum one must change the mass or velocity or both

 

[Air Force Brat]

I do not intend to be dragged into this kind of discussion again but for correction sake, the author of the above linked article made an error in saying that the rudder loses effectiveness at high AOA. It should be the elevators that loses effectiveness or controllability at high AOA, something which we already know and something which doesn't apply to canards. Suffice to say we've discussed a number of times previously on how the canards have an advantage in this kind of situation over the tail control surfaces/elevators mainly by referencing the explanation on the subject in Dr Song's paper.

Actually Quickie the vertical stab does loose effectiveness along with the Rudder, that is why the J-20 has ventral fin below the wing and vertical stab to maintain directional stability at high angle of Attack, while the elevator may have reaced the limit of its ability to further increase pitch, it is still capable of decreasing pitch, the canard suffers the same limitations at low airspeed high angles of attack, OVT is still producing thrust and thus is still "active" as pitch control.Brat

 

[ahadicow]

Today I witnessed a single person, through sheer willpower and absurdity of argument, manage to twist simple and elementry physics at a most fundamental level. It is as if the stable and farmilar universe established by classical physics no longer hold any meaning nor bear any relations to the reality and we, through the imaginative and fantastical brilliance of this brave young man, entered a whole new age, a age when the force, energy and momentum fell aside to the beautiful clearity, the profound truth and the exquisite elegency of this one single concept: vector. gentleman, please stand with me and behold the begining of a new imaginary physics, the physics of vector thrust.

 

[MiG-29]

Today I witnessed a single person, through sheer willpower and absurdity of argument, manage to twist simple and elementry physics at a most fundamental level. It is as if the stable and farmilar universe established by classical physics no longer hold any meaning nor bear any relations to the reality and we, through the imaginative and fantastical brilliance of this brave young man, entered a whole new age, a age when the force, energy and momentum fell aside to the beautiful clearity, the profound truth and the exquisite elegency of this one single concept: vector. gentleman, please stand with me and behold the begining of a new imaginary physics, the physics of vector thrust.

what i can say

 

[duncanidaho]

Re: J-20 The New Generation Fighter Thread IV

hahaha

Look first study physics, any force is a vector, TVC nozzles is another vector, lift is a vector, we call that vector lift because it is the product of air flows, but TVC nozzles is also air flow hahahaha.

we call it lift just because its direction is opposite to the gravity, with thrust vectoring you are aiding the wing`s lift

hahahah

Your eyes can not believe you are adding lift to thrust sin(c) hahahaha yeah add lift vector the thrust vector hahahahah

hahahaha

Sorry, but I think you still don't now what Lift is. The Lifts direction isn't the opposite of gravity. Lift may point upward in the aerodynamic, but it also may point horizontal (like the sail of a sailing-vessel) or it may point downward ( like a spoiler of a Formular1 Race-car). To create lift you need a medium like air, therefore you can't aid the wings lift by thrust vectoring.

You give us alot of explanation, but it does not change the fact that your assumption, that thrust vectoring creates lift, wrong is.

 

[MiG-29]

Re: J-20 The New Generation Fighter Thread IV

Sorry, but I think you still don't now what Lift is. The Lifts direction isn't the opposite of gravity. Lift may point upward in the aerodynamic, but it also may point horizontal (like the sail of a sailing-vessel) or it may point downward ( like a spoiler of a Formular1 Race-car). To create lift you need a medium like air, therefore you can't aid the wings lift by thrust vectoring.

You give us alot of explanation, but it does not change the fact that your assumption that thrust vectoring creates lift wrong is.

you do not understand it because you do not see it as vectors, you see lift as wing lift, not as vector, as long as you do not see it as a vector system you won`t understand.

The formula says

Vertical: L - W + T sin(c) = Fv

lift minus weight plus the product thrust sin of angle C.

that is the vertical force, and forces are vectors, plus i am just quoting what nasa says.

If you can not understand it, do not take me wrong but read a bit of Linear Algebra, otherwise you will not understand what the nasa pages says.

 

[Engineer]

Re: J-20 The New Generation Fighter Thread IV

look your fantasy and lack of knowledge does not pass a physics test let us see what is momentum

Look at you. You so desperately need to put down J-20 that you invented myths to claim thrust vectoring helps an aircraft turn. Now that your myths have been exposed, you ignore basic physics by treating force, moment, and momentum as the same thing. In real world physics, they are different quantities with different units. Force has a unit of Newton (N). Moment has a unit of Newton-meter (N m). Momentum has a unit of Newton-second (N s).

Momentum is a vector quantity. As discussed in an earlier unit, a vector quantity is a quantity that is fully described by both magnitude and direction

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Your myths have already been exposed. Bringing up vector is irrelevant since it has been shown thrust vectoring doesn't produce aerodynamics lift that helps when an aircraft is turning. That is because thrust vectoring is a moment producing effector, not a force producing effector. Pitching-up with thrust vectoring decreases lift coefficient, contrary to your claim that thrust vectoring increases lift.

Vectoring was intended primarily as a moment-producing effector, so vectoring the plume up would cause a noseup pitching moment. But the exhaust plume vectored up would decrease the lift coefficient in the adverse direction while increasing the pitching moment coefficient in the proverse direction.

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so now

Let me repeat you once more



The gases coming out of the vector nozzle help push the airplane's nose up or down. This vectoring increases the roll rate of the plane by 50 percent, making it much more maneuverable than other fighters=Vectoring was intended primarily as a moment-producing effector, so vectoring the plume up would cause a noseup pitching moment.But the exhaust plume vectored up would decrease the lift coefficient in the adverse direction while increasing the pitching moment coefficient in the proverse direction. This behavior is analogous to a blown flap=Today’s most maneuverable fighters use thrust vectoring, which can make a jet turn faster and more tightly .

No. Let me repeat to you. Your quote says from the paper says pitch-up moment causes decrease in lift coefficient. Given that pitch-up occurs when the aircraft is in a turn, so this means thrust vectoring doesn't add lift to increase turn rate. From

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:

Vectoring was intended primarily as a moment-producing effector, so vectoring the plume up would cause a noseup pitching moment. But the exhaust plume vectored up would decrease the lift coefficient in the adverse direction while increasing the pitching moment coefficient in the proverse direction.

 

[Quickie]

Actually Quickie the vertical stab does loose effectiveness along with the Rudder, that is why the J-20 has ventral fin below the wing and vertical stab to maintain directional stability at high angle of Attack, while the elevator may have reaced the limit of its ability to further increase pitch, it is still capable of decreasing pitch, the canard suffers the same limitations at low airspeed high angles of attack, OVT is still producing thrust and thus is still "active" as pitch control.Brat

Yes, the vertical stabilizers and rudders will loose effectivenes at high AOA but not as much as the elevators. They go all the way to the point of total loss of effectiveness when it goes into a stall. During a stall, the elevators could already be stalling or starting to loose much of its effectiveness. Pitching the elevators up will only increase the stalling or loss of effectiveness. The canards, being on the other side of the CG, do not have this problem because it's positively deflected at the aircraft's high AOA. Deflecting the canards negatively, for example to bring the aircraft out of stall, in this case does not have the effect of stalling the canards further or reducing its effectiveness.

 

[Engineer]

Momentum is a vector quantity. As discussed in an earlier unit, a vector quantity is a quantity that is fully described by both magnitude and direction

So go and read more

Your myths have already been exposed. Bringing up vector is irrelevant since it has been shown thrust vectoring doesn't produce aerodynamics lift that helps when an aircraft is turning. That is because thrust vectoring is a moment producing effector, not a force producing effector.

Torque and angular momentum are actually vector
quantities. Angular momentum is conserved in both magnitude and direction in the
absence of external torque

Please, Log in or Register to view URLs content!

There are four forces that act on an aircraft in flight: lift, weight, thrust, and drag. The motion of the aircraft through the air depends on the relative size of the various forces and the orientation of the aircraft. For an aircraft in cruise, the four forces are balanced, and the aircraft moves at a constant velocity and altitude. Some modern fighter aircraft can change the angle of the thrust by using a movable nozzle. The ability to change the angle of the thrust is called thrust vectoring, or vectored thrust.

Forces are vector quantities having a magnitude and a direction. The resulting acceleration, velocity and displacement of the aircraft are also vector quantities which can be determined by Newton's second law of motion and the rules of vector algebra. There are two component equations for the force on an aircraft. One equation gives the the net vertical force Fv, and the other gives the net horizontal force Fh. If we denote the thrust by the symbol T, the lift by L, the drag by D, and the weight by W, the usual force equations for an aircraft in level flight are:

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Torque is not a force. No matter how you many times you repeat the word "vectors", torque does not equate to force, and thrust vectoring does not produce aerodynamics lift while an aircraft is turning. Going off tangent with three paragraphs of irrelevant technical material is known as a fallacy called

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. It is described as "cases in which scientific evidence is thrown aside in favour of a litany of tragic individual cases presented to the public by articulate advocates who pose as experts in their field.

With new mechanical systems it is possible to deflect the engine exhaust from the nozzle and cant the thrust vector at an angle. We will call this angle c. The resulting force equations are shown on the slide:

Vertical: L - W + T sin(c) = Fv

Horizontal: T cos(c) - D = Fh

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The problem with the above equations is that they treat the aircraft as a point. In the real world, the nozzle is not at the aircraft's center-of-gravity, hence thrust vectoring produces thrust components resulting in torque. In fact, a NASA paper you quoted notes that thrust vectoring is a moment-producing effector.

Vectoring was intended primarily as a moment-producing effector, so vectoring the plume up would cause a noseup pitching moment. But the exhaust plume vectored up would decrease the lift coefficient in the adverse direction while increasing the pitching moment coefficient in the proverse direction.

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